U.S. patent application number 14/820628 was filed with the patent office on 2016-02-25 for receiver, communication device, and communication method.
This patent application is currently assigned to Renesas Electronics Corporation. The applicant listed for this patent is Renesas Electronics Corporation. Invention is credited to Shunichi KAERIYAMA, Hirokazu NAGASE, Koichi TAKEDA.
Application Number | 20160056850 14/820628 |
Document ID | / |
Family ID | 55349195 |
Filed Date | 2016-02-25 |
United States Patent
Application |
20160056850 |
Kind Code |
A1 |
NAGASE; Hirokazu ; et
al. |
February 25, 2016 |
RECEIVER, COMMUNICATION DEVICE, AND COMMUNICATION METHOD
Abstract
To provide a receiver, a communication device, and a
communication method capable of restoring a signal transmitted via
a non-contact transmission channel with high accuracy. A
communication device has a transmission circuit that converts an
input signal into a pulse, a non-contact transmission channel that
has a primary side coil and a secondary side coil and transmits the
pulse from the transmission circuit in a non-contact manner, a
restoration circuit that restores the input signal on the basis of
a reception signal corresponding to the pulse transmitted via the
non-contact transmission channel, an initialization unit that
initializes an output of the non-contact transmission channel, and
an initialization control unit that outputs a control signal of
controlling the initialization unit on the basis of the reception
signal corresponding to the pulse received via the non-contact
transmission channel.
Inventors: |
NAGASE; Hirokazu; (Tokyo,
JP) ; TAKEDA; Koichi; (Tokyo, JP) ; KAERIYAMA;
Shunichi; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Renesas Electronics Corporation |
Tokyo |
|
JP |
|
|
Assignee: |
Renesas Electronics
Corporation
Tokyo
JP
|
Family ID: |
55349195 |
Appl. No.: |
14/820628 |
Filed: |
August 7, 2015 |
Current U.S.
Class: |
375/340 |
Current CPC
Class: |
H03K 5/04 20130101; H03K
17/61 20130101 |
International
Class: |
H04B 1/10 20060101
H04B001/10; H03K 5/04 20060101 H03K005/04; H04B 1/16 20060101
H04B001/16 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 25, 2014 |
JP |
2014-170758 |
Claims
1. A communication device comprising: a transmission circuit that
converts an input signal into a pulse; a non-contact transmission
channel that includes an AC coupling element and transmits the
pulse from the transmission circuit in a non-contact manner; a
restoration circuit that restores the input signal on a basis of a
reception signal corresponding to the pulse transmitted via the
non-contact transmission channel; an initialization unit that
initializes an output of the non-contact transmission channel; and
an initialization control unit that outputs a control signal of
controlling the initialization unit on a basis of the reception
signal corresponding to the pulse received via the non-contact
transmission channel.
2. The communication device according to claim 1, further
comprising a widening circuit that increases a pulse width of the
pulse received via the non-contact transmission channel, wherein
the restoration circuit restores the input signal on a basis of the
received pulse, the pulse width of which is increased by the
widening circuit.
3. The communication device according to claim 1, further
comprising a circuit that adjusts at least one of a timing and a
period of the initialization performed by the initialization
unit.
4. The communication device according to claim 1, wherein the
initialization unit is connected to both ends of the AC coupling
element on a reception side of the non-contact transmission
channel.
5. The communication device according to claim 1, wherein the
initialization unit includes a transistor connected to a reception
side of the non-contact transmission channel, the initialization
control unit performs on/off control for the transistor, and the
transistor is turned on, thereby performing initialization.
6. The communication device according to claim 1, wherein the
reception signal includes a main pulse and a counter pulse
corresponding to the pulses transmitted through the non-contact
transmission channel, the counter pulse has a polarity opposite to
the main pulse and is continuous with the main pulse, and the
restoration circuit restores the input signal in accordance with
the polarity of the main pulse.
7. The communication device according to claim 1, wherein, to the
non-contact transmission channel, a high-pass filter connected to
the AC coupling element is provided.
8. A communication method comprising: converting an input signal
into a pulse in a transmission circuit; transmitting the pulse from
the transmission circuit to a reception circuit in a non-contact
manner via a non-contact transmission channel including an AC
coupling element; restoring the input signal on a basis of a
reception signal corresponding to the pulse transmitted via the
non-contact transmission channel; generating a control signal on a
basis of the reception signal corresponding to the pulse received
via the non-contact transmission channel; and initializing an
output of the non-contact transmission channel on a basis of the
control signal.
9. The communication method according to claim 8, further
comprising: increasing a pulse width of the pulse received via the
non-contact transmission channel; and restoring the input signal on
a basis of the received pulse, the pulse width of which is
increased.
10. The communication method according to claim 8, further
comprising adjusting at least one of a timing and a period of
performing the initialization.
11. The communication method according to claim 8, wherein, to both
ends of the AC coupling element on a reception side of the
non-contact transmission channel, an initialization unit that
performs the initialization is connected.
12. The communication method according to claim 8, wherein, a
transistor is connected to a reception side of the non-contact
transmission channel, the transistor is on/off controlled in
accordance with the control signal, and the initialization is
performed by turning on the transistor.
13. The communication method according to claim 8, wherein the
reception signal includes a main pulse and a counter pulse
corresponding to the pulses transmitted through the non-contact
transmission channel, the counter pulse has a polarity opposite to
the main pulse and is continuous with the main pulse, and the input
signal is restored in accordance with the polarity of the main
pulse.
14. The communication method according to claim 8, wherein, to the
non-contact transmission channel, a high-pass filter connected to
the AC coupling element is provided.
15. A receiver comprising: a restoration circuit that restores an
input signal on a basis of a reception signal corresponding to a
pulse transmitted via a non-contact transmission channel including
an AC coupling element; an initialization unit that initializes an
output of the non-contact transmission channel; and an
initialization control unit that outputs a control signal of
controlling the initialization unit on a basis of the reception
signal corresponding to the pulse received via the non-contact
transmission channel.
16. The receiver according to claim 15, further comprising a
widening circuit that increases a pulse width of the pulse received
via the non-contact transmission channel, wherein the restoration
circuit restores the input signal on a basis of the received pulse,
the pulse width of which is increased by the widening circuit.
17. The receiver according to claim 15, further comprising a
circuit that adjusts at least one of a timing and a period of the
initialization performed by the initialization unit.
18. The receiver according to claim 15, wherein the initialization
unit is connected to both ends of the AC coupling element on a
reception side of the non-contact transmission channel.
19. The receiver according to claim 15, wherein the initialization
unit includes a transistor connected to a reception side of the
non-contact transmission channel, the initialization control unit
performs on/off control for the transistor, and the transistor is
turned on, thereby performing the initialization.
20. The receiver according to claim 15, wherein the reception
signal includes a main pulse and a counter pulse corresponding to
the pulses transmitted through the non-contact transmission
channel, the counter pulse has a polarity opposite to the main
pulse and is continuous with the main pulse, and the restoration
circuit restores the input signal in accordance with the polarity
of the main pulse.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from Japanese patent application No. 2014-170758, filed on
Aug. 25, 2014, the disclosure of which is incorporated herein in
its entirety by reference.
BACKGROUND
[0002] The present invention relates to a receiver, a communication
device, and a communication method.
[0003] Japanese Unexamined Patent Application Publication No.
2001-111390 discloses a pulse isolator. The pulse isolator
disclosed in Japanese Unexamined Patent Application Publication No.
2001-111390 uses a pulse transformer. Using this makes it possible
to transmit a pulse signal while insulation is achieved between
input and output terminals. Specifically, when an input pulse
signal is supplied, at a rising edge and a falling edge of the
input pulse signal, a current flows in a primary winding of the
pulse transformer. Therefore, a voltage is induced at both ends of
a secondary winding of the pulse transformer.
[0004] Further, on a secondary side of the pulse transformer, a
resistor for suppressing ringing is provided. That is, the both
ends of the secondary winding are connected through the
resistor.
SUMMARY
[0005] In the pulse isolator disclosed in Japanese Unexamined
Patent Application Publication No. 2001-111390, the both ends of
the secondary winding are connected through the resistor. This
causes attenuation of an output pulse signal and hinders normal
communication.
[0006] The other problems and novel features are revealed by the
description of this specification and the attached drawings.
[0007] According to an aspect of the present invention, a
communication device includes a restoration circuit that restores
an input signal on the basis of a reception signal corresponding to
a pulse transmitted via a non-contact transmission channel, an
initialization unit that initializes an output of the non-contact
transmission channel, and an initialization control unit that
outputs a control signal that controls the initialization unit on
the basis of the reception signal corresponding to the pulse
received via the non-contact transmission channel.
[0008] According to the aspect, it is possible to restore a signal
transmitted via the non-contact transmission channel with high
accuracy.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The above and other aspects, advantages and features will be
more apparent from the following description of certain embodiments
taken in conjunction with the accompanying drawings, in which:
[0010] FIG. 1 is a circuit diagram showing the structure of a
communication device including a non-contact transmission
channel;
[0011] FIG. 2 is a timing chart showing signal waveforms in the
communication device shown in FIG. 1;
[0012] FIG. 3 is a timing chart showing signal waveforms in the
communication device shown in FIG. 1;
[0013] FIG. 4 is a diagram showing the schematic structure of the
communication device;
[0014] FIG. 5 is a timing chart showing signal waveforms of the
communication device shown in FIG. 4;
[0015] FIG. 6 is a block diagram showing the structure of a
communication device according to a first embodiment;
[0016] FIG. 7 is a timing chart showing signal waveforms of the
communication device according to the first embodiment;
[0017] FIG. 8 is a circuit diagram showing an example of the
structure of the communication device according to the first
embodiment;
[0018] FIG. 9 is a timing chart showing signal waveforms in a case
where initialization is not performed;
[0019] FIG. 10 is a timing chart showing signal waveforms in a case
where the initialization is performed;
[0020] FIG. 11 is a block diagram showing the structure of a
communication device according to a second embodiment;
[0021] FIG. 12 is a timing chart showing signal waveforms of the
communication device according to the second embodiment;
[0022] FIG. 13 is a diagram showing an example of the structure of
a main part in the communication device according to the second
embodiment;
[0023] FIG. 14 is a circuit diagram showing an example of the
structure of a widening circuit;
[0024] FIG. 15 is a circuit diagram showing an example of the
structure of a comparator;
[0025] FIG. 16 is a block diagram showing the structure of a
communication device according to a third embodiment;
[0026] FIG. 17 is a timing chart showing signal waveforms of the
communication device according to the third embodiment;
[0027] FIG. 18 is a diagram simply showing the structure of
restoring a signal in accordance with a pulse polarity;
[0028] FIG. 19 is a timing chart in a case where the signal is
restored in accordance with the pulse polarity;
[0029] FIG. 20 is a diagram simply showing the structure of
restoring a signal in accordance with a pulse count;
[0030] FIG. 21 is a timing chart in a case where the signal is
restored in accordance with the pulse count;
[0031] FIG. 22 is a diagram simply showing the structure of
restoring a signal by using an SR logic circuit;
[0032] FIG. 23 is a timing chart in a case where the signal is
restored by using the SR logic circuit; and
[0033] FIG. 24 is a diagram showing an example of application of
the communication device according to the embodiments.
DETAILED DESCRIPTION
[0034] To make explanation clear, the following description and the
figures are appropriately omitted and simplified. Further,
components indicated in the figures as functional blocks that
perform various processes can be structured by a CPU, a memory, and
other circuits as hardware and are achieved by a program or the
like loaded to the memory as software. Therefore, persons skilled
in the art understand that those functional blocks can be achieved
only by hardware or software or by combination of those in various
forms, and are not limited to one of those. It should be noted that
in the figures, the same components are denoted by the same
symbols, an overlapped explanation is omitted as necessary.
[0035] First, the structure and operation of a communication device
including a non-contact transmission channel will be described with
reference to FIGS. 1 to 3. FIG. 1 is a circuit diagram showing the
structure of a communication device 200, and FIG. 2 and FIG. 3 are
timing charts showing signal waveforms of the communication device
200. FIG. 2 and FIG. 3 show the signal waveforms at terminals A to
S shown in FIG. 1. That is, signals at the terminals A to S will be
described as signals A to S as appropriate.
[0036] As shown in FIG. 1, the communication device 200 includes a
transmission circuit 210, a non-contact transmission channel 220,
and a reception circuit 230. The communication device 200 is a
pulse isolator or the like and transmits a signal via the
non-contact transmission channel 220. That is, the signal
transmitted from the transmission circuit 210 is received by the
reception circuit 230 via the non-contact transmission channel
220.
[0037] The transmission circuit 210 includes an inverting amplifier
213, an edge detection circuit 214, an edge detection circuit 215,
AND circuits 216 to 218, and an inverting amplifier 219. The
non-contact transmission channel 220 includes a primary side coil
221, a secondary side coil 222, a filter 223, and a filter 224. The
reception circuit 230 includes a restoration circuit 235. The
restoration circuit 235 includes a comparator 231, a comparator
232, a widening circuit 233, a widening circuit 234, a
determination circuit 236, and a latch circuit 237.
[0038] The transmission circuit 210 is a circuit that converts an
input signal IN into a transmission pulse. The transmission pulse
generated in the transmission circuit 210 is received by the
reception circuit 230 via the non-contact transmission channel 220.
The restoration circuit 235 of the reception circuit 230 restores
the signal by using a reception pulse received via the non-contact
transmission channel 220.
[0039] The input signal IN is split into two signals. One of the
input signal IN is input to the edge detection circuit 214 via the
inverting amplifier 213, and the other of the input signal IN is
input to the edge detection circuit 215. The edge detection circuit
214 and the edge detection circuit 215 detect a rising edge of the
signal. Therefore, when the input signal IN shown in FIG. 2 is
input to the transmission circuit 210, output signals from the edge
detection circuit 214 and the edge detection circuit 215 show
signal waveforms indicated as A and B of FIG. 2, respectively. The
signals A and B from the edge detection circuit 214 and the edge
detection circuit 215 are input to the AND circuit 216. The AND
circuit 216 outputs AND of the signal A and the signal B to the AND
circuits 217 and 218. The output from the AND circuit 216 is
indicated as a signal C shown in FIG. 2. The signal C from the AND
circuit 216 includes a rising pulse corresponding to the rising
edge of the input signal IN and a falling pulse corresponding to
the falling edge thereof.
[0040] To the AND circuit 217, the signal C from the AND circuit
216 and a signal from the inverting amplifier 213 are input.
Therefore, the AND circuit 217 outputs AND of the signal C and an
inversion signal of the input signal IN. The output of the AND
circuit 217 is amplified by the inverting amplifier 219 having
three stages, thereby generating a signal D shown in FIG. 2. To the
AND circuit 218, the signal C of the AND circuit 216 and the input
signal IN are input. Therefore, the AND circuit 217 outputs AND of
the signal C and the input signal IN. The output of the AND circuit
218 is amplified by the inverting amplifier 219 having the three
stages, thereby generating a signal E shown in FIG. 2.
[0041] The transmission circuit 210 transmits the signal D and the
signal E to the non-contact transmission channel 220. The
non-contact transmission channel 220 includes the primary side coil
221, the secondary side coil 222, the filter 223, and the filter
224. The primary side coil 221 and the secondary side coil 222 form
an insulation transformer with an insulation boundary intervened
therebetween. Further, the secondary side coil 222 is connected to
VDD by a center tap. To one end of the primary side coil 221, the
signal D is supplied, and to the other end thereof, the signal E is
supplied.
[0042] Therefore, a current F corresponding to the signal D and the
signal E flows through the primary side coil 221 (see F shown in
FIG. 2). At a timing corresponding to the rising edge of the input
signal IN or the falling edge thereof, the pulse-like current F
flows through the primary side coil 221. Further, at the rising
edge of the input signal IN, a direction of the current F that
flows through the primary side coil 221 is opposite to that at the
falling edge thereof. As a result, it is possible to convert edge
information of the input signal IN to a polarity of the
transmission pulse.
[0043] In the secondary side coil 222, a differential voltage
corresponding to the current F is induced. The differential voltage
G is shown as a signal G of FIG. 2 and FIG. 3. In the differential
voltage G, an edge pulse (main pulse) and a counter pulse exist.
The edge pulse corresponds to the edge of the input signal IN. The
counter pulse appears immediately after the edge pulse. The counter
pulse has the polarity opposite to the edge pulse and appears as a
pair with the edge pulse. In the differential voltage G, the edge
pulse having a positive polarity corresponding to the rising edge
of the input signal IN and the edge pulse having a negative
polarity corresponding to the falling edge of the input signal IN.
Further, immediately after the edge pulse having the positive
polarity, the counter pulse having the negative polarity exists,
and immediately after the edge pulse of the negative polarity, the
counter pulse of the positive polarity exists.
[0044] One end of the secondary side coil 222 is connected to the
filter 223, and the other end thereof is connected to the filter
224. The filter 223 and the filter 224 are high-pass filters (HPF)
including R and C, for example. The filter 223 and the filter 224
remove a noise component from a reception pulse received via the
non-contact transmission channel 220. The signals that pass through
the filters 223 and 224 are output to the comparator 231 and 232,
respectively.
[0045] In the comparator 231, an output signal of the filter 223 is
input to a non-inverting input terminal, and an output signal of
the filter 224 is input to the inverting input terminal. Therefore,
the comparator 231 detects a pulse having a positive polarity of
the differential voltage G. The output of the comparator 231 shows
a waveform of a signal H shown in FIG. 3. In the comparator 232,
the output of the filter 223 is input to the inverting input
terminal, and the output of the filter 224 is input to the
non-inverting input terminal. Therefore, the comparator 231 detects
a pulse having a negative polarity of the differential voltage G.
The output of the comparator 232 shows a waveform of a signal J
shown in FIG. 3. The signal H includes a pulse corresponding to the
pulse having the positive polarity of the differential voltage G.
The signal J includes a pulse corresponding to the pulse having the
negative polarity of the differential voltage G. The comparators
231 and 232 function as difference amplifiers with both terminals
of the secondary side coil 222 as differential inputs.
[0046] The signal H from the comparator 231 is input to the
widening circuit 233. The signal J from the comparator 232 is input
to the widening circuit 234. The widening circuits 233 and the
widening circuit 234 increase pulse widths of the input signals H
and J, respectively. That is, the widening circuit 233 and the
widening circuit 234 are delay circuits that output the rising edge
at high speed and delay and output the falling edge. As a result,
it is possible to delay the falling edge of the pulse. Thus, the
widening circuit 233 increases the pulse width of the pulse
included in the signal H. The widening circuit 234 increases the
pulse width of the pulse included in the signal J. Therefore, the
output from the widening circuit 233 and the output from the
widening circuit 234 show waveforms of a signal I and a signal K
shown in FIG. 3, respectively.
[0047] The signal I from the widening circuit 233 and the signal K
from the widening circuit 234 are input to the determination
circuit 236. The determination circuit 236 is a circuit that
determines which pulse of the signal I and the signal K gets
thereto first. The determination circuit 236 includes a flip-flop
circuit 236a, a flip-flop circuit 236b, an AND circuit 236c, and an
AND circuit 236d. The flip-flop circuit 236a and the flip-flop
circuit 236b are each an RS flip-flop circuit that gives priority
to S.
[0048] The signal I from the widening circuit 233 is input to an S
terminal of the flip-flop circuit 236b and the AND circuit 236c.
Further, the signal I from the widening circuit 233 is inverted and
input to an R terminal of the flip-flop circuit 236a. The signal K
from the widening circuit 234 is input to an S terminal of the
flip-flop circuit 236a and the AND circuit 236d. Further, the
signal K from the widening circuit 233 is inverted and input to an
R terminal of the flip-flop circuit 236b.
[0049] The flip-flop circuit 236a is set at K=1 and reset at I=0.
The flip-flop circuit 236b is set at I=1 and reset at K=0.
Therefore, the signal from the flip-flop circuit 236a and the
signal from the flip-flop circuit 236b show waveforms of a signal L
and a signal M shown in FIG. 3, respectively.
[0050] The signal L from the flip-flop circuit 236a is inverted and
input to the AND circuit 236c. The signal M from the flip-flop
circuit 236b is inverted and input to the AND circuit 236d.
Therefore, an output of the AND circuit 236c and an output of the
AND circuit 236d are waveforms of a signal S and a signal R shown
in FIG. 3, respectively. The signal S from the AND circuit 236c and
the signal R from the AND circuit 236d are inverted and input to
the latch circuit 237. The latch circuit 237 includes two NAND
circuits.
[0051] An output signal OUT from the latch circuit 237 is such a
pulse signal that the rise of a pulse of the signal S is set as the
rising edge, and the rising edge of a pulse of the signal R is set
as the falling edge. Thus, the output signal OUT from the latch
circuit 237 is a signal equivalent to the input signal IN. In this
way, the restoration circuit 235 restores the input signal IN. A
part or all of the communication device 200 and the communication
method described above can be used in the embodiments to be
described later.
[0052] In this way, in the communication device 200 such as an
isolator, the transmission circuit 210 extracts the edge part from
the input signal IN and generates a rising pulse and a falling
pulse. Then, with the rising pulse and the falling pulse, the
direction of the current F that flows through the primary side coil
221 is changed. That is, edge information related to the rising
edge and the falling edge of the input signal IN is converted to
the polarity of a reception pulse. For example, at the rising edge
of the input signal IN, the differential voltage G becomes an edge
pulse having the positive polarity, and at the falling edge, the
differential voltage G becomes an edge pulse having the negative
polarity. In this way, the polarity of the differential voltage G
is changed between the rising edge and the falling edge of the
input signal IN.
[0053] In the communication device 200 as described above, when the
counter pulse on the reception side is extended, the pulse
interferes with a subsequent edge pulse. As a result, there is a
fear that Hi/Lo information may be lost, and the restoration
circuit 235 may perform erroneous restoration. This causes a
problem in that a delay reduction and achievement of high data rate
are interfered. On the other hand, components other than the main
pulse included in the differential voltage G is an unnecessary
component for the restoration of the signal.
[0054] Subsequently, with reference to FIG. 4 and FIG. 5, the
problem mentioned above will be described. FIG. 4 is a block
diagram simply showing the structure of the communication device
200. FIG. 5 is a timing chart showing signal waveforms in the
communication device. That is, FIG. 5 shows the signal waveforms at
terminals A to L shown in FIG. 4. Note that the content shared with
FIGS. 1 to 3 will be omitted.
[0055] The transmission circuit 210 includes a pulse generation
circuit 211 and a pulse generation circuit 212. The pulse
generation circuit 211 generates a rising pulse corresponding to
the rising edge of an input signal A. That is, the pulse generation
circuit 212 generates a falling pulse corresponding to the falling
edge of a reception signal A. Therefore, an output from the pulse
generation circuit 211 and an output from the pulse generation
circuit 212 show waveforms of a signal B and a signal C shown in
FIG. 5, respectively.
[0056] The signal B from the pulse generation circuit 211 is
supplied to one end of the primary side coil 221, and the signal C
from the pulse generation circuit 212 is supplied to the other end
of the primary side coil 221. As a result, a current corresponding
to a differential voltage between the signal B and the signal C
flows through the primary side coil 221. Through the primary side
coil 221, a current having an opposite polarity between the rising
pulse of the signal B and the falling pulse of the signal C
flows.
[0057] A voltage corresponding to the current that flows through
the primary side coil 221 is generated in the secondary side coil
222. In the secondary side coil 222, a voltage with a polarity
corresponding to the direction of the current is induced. In the
secondary side coil 222, a voltage having the edge information is
induced. The voltage generated in the secondary side coil 222 shows
a waveform of a voltage D-E shown in FIG. 5. The voltage D-E
includes an edge pulse P1 corresponding to the rising edge of the
input signal A and an edge pulse P3 corresponding to the falling
edge thereof. Immediately after the edge pulse P1 having the
positive polarity, a counter pulse P2 having the negative polarity
is generated, and immediately after the edge pulse P3 having the
negative polarity, a counter pulse P4 having the positive polarity
is generated.
[0058] In the same way as shown in FIG. 1, to one end of the
secondary side coil 222, the filter 223 is connected, and to the
other end thereof, the filter 224 is connected. The filter 223 and
the filter 224 are high-pass filters that remove common mode noise
at a low frequency.
[0059] A signal F that passes through the filter 223 and a signal G
that passes through the filter 224 are input to the comparators 231
and 232, respectively, in the same way as shown in FIG. 1. Then,
the comparator 231 and the comparator 232 separate the edge pulse
and the counter pulse for each polarity. An output of the
comparator 231 and an output of the comparator 232 are widened by
the widening circuits 233 and 234, respectively.
[0060] For example, in an isolator applied to an IGBT (Insulated
Gate Bipolar Transistor) driver, in association with switching of
the IGBT, a difference is generated between reference potentials of
a controller-side chip (transmission circuit 210) and an IGBT-side
chip (reception circuit 230) by approximately 1 kV. The variation
of the reference potentials propagates through an inter-transformer
parasitic capacitance, so a common mode noise is mixed in the
signal D and signal E. However, generally, the frequency of the
noise is lower than a signal component, so the noise can be removed
by the filters 223 and 224. In the signal F that has passed through
the filter 223 and the signal G that has passed through the filter
224, the edge pulse as a main body of the edge information and the
counter pulse having the opposite polarity which is generated
immediately after that are mixed. The two comparators 231 and 232
separate the edge pulse and the counter pulse for each
polarity.
[0061] It should be noted that the filters 223 and 224 also serve a
function of determining operation points of the comparators 231 and
232. The edge pulse included in the outputs of the comparators 231
and 232 are widened by the widening circuits 233 and 234.
[0062] Signals J and K from the widening circuits 233 and 234 are
input to the determination circuit 236. The counter pulse
unnecessary for the signal restoration is generated immediately
after the edge pulse. For example, the determination circuit 236
determines which is a first comer, and thus the restoration circuit
235 restores the input signal A. The signal is processed on the
basis of the first-comer determination logic, with the result that
the input signal A is restored to obtain an output signal L.
[0063] The above description is a communication principle of the
isolator. However, as described above, in the signal D and the
signal E from the secondary side coil 222, the common mode noise
may be generated. The common mode noise is generated on both the
signal D and the signal E in the same way. Therefore, basically, it
is possible to remove the common mode noise by a differential
structure. However, different amounts of common mode noise may be
generated on the signal D and the signal E in some cases. A signal
waveform in this case is shown in FIG. 5 in an enlarged manner. As
shown in the enlarged diagram of the signal D-E of FIG. 5, when a
difference is generated between the common mode noises on the
signal D and the signal E, a noise is generated between the counter
pulse P2 and the edge pulse P3.
[0064] As shown in the enlarged diagram of FIG. 5, the common mode
noise also includes a counter component. For example, when the
common mode noise having the positive polarity is generated, a
counter component having the negative polarity is generated
immediately after that. A frequency component of the common mode
noise is low, so an amplitude becomes small, but the width of the
noise is increased.
[0065] In the case where the common mode noise as described above
is generated, it may be impossible to lower a threshold value. That
is, to detect a reception signal by the reception circuit 230,
lowering the threshold value is effective. However, in the case
where the common mode noise is generated, when the threshold value
is lowered, this responds to the common mode noise. As a result,
malfunction of the reception circuit 230 is caused. Such a common
mode noise has a low frequency and thus can be removed by the
high-pass filter. However, when the noise passes through the
high-pass filter of RC, swinging back is caused in the signal
waveform.
[0066] In the process in which the counter pulse that has passed
through the filters 223 and 224 is attenuated, in the waveform, the
swinging back may be caused again to the side of the polarity of
the edge pulse beyond 0 level in some cases (see, broken line of
F-G shown in FIG. 5). The swinging back is caused due to a
transient property of the filters 223 and 224 of RC. Because of the
swinging back, in the outputs of the comparators 231 and 232 or the
outputs of the widening circuits 233 and 234, there is a fear that
the pulse width may be increased (see, signals J and K shown in
FIG. 5). Therefore, an interval of the input pulses to the
determination circuit 236 is reduced. Before the determination
circuit 236 terminates the process for the edge pulse and returns
to a standby state, if the next edge pulse reaches the circuit, it
may be impossible to distinguish the edge pulse from the counter
pulse, and thus the signal restoration is mistaken (see, signal L
shown in FIG. 5).
[0067] As described above, in the case where the swinging back
indicated as the broken line of F-G, in the outputs J and K of the
widening circuits 233 and 234, the pulse is generated even during a
period of the swinging back. Therefore, when the pulse width is
increased, pulses are interfered with each other, with the result
that the signal restoration is difficult to be performed. In
particular, in the case where communication is performed at a high
data rate, pulses are easily interfered with each other, so it is
difficult to perform the signal restoration. Note that, in Japanese
Unexamined Patent Application Publication No. 2001-111390, the
swinging back can be attenuated, but the edge pulse is also
attenuated. As a result, there is a fear that the restoration
circuit 235 may perform erroneous signal restoration.
[0068] In view of the above, in this embodiment, the reception
circuit initializes the reception signal. Note that the
initialization of the reception signal means that the reception
signal is attenuated or deleted. This process reliably makes it
possible to restore the signal. Therefore, it is possible to reduce
a delay and achieve a higher data rate.
First Embodiment
[0069] A communication device 100 according to this embodiment will
be described with reference to FIG. 6. FIG. 6 is a block diagram
showing the structure of the communication device 100. FIG. 7 is a
timing chart showing signal waveforms at terminals A to L shown in
FIG. 6. The communication device 100 includes a transmission
circuit 10, a non-contact transmission channel 20, and a reception
circuit 30. The reception circuit 30 includes a restoration circuit
35, an initialization control unit 40, and an initialization unit
50.
[0070] Like the communication device 200 shown in FIG. 1, the
communication device 100 is a pulse isolator or the like and
transmits a signal via the non-contact transmission channel 20. The
non-contact transmission channel 20 includes a primary side coil 21
and a secondary side coil 22 that are AC coupling elements. The
signal transmitted from the transmission circuit 10 is received by
the reception circuit 30 via the non-contact transmission channel
20. The transmission circuit 10, the non-contact transmission
channel 20, and the restoration circuit 35 have the same structures
as the transmission circuit 210, the non-contact transmission
channel 220, and the restoration circuit 235, respectively, shown
in FIG. 1 or FIG. 4, so descriptions thereof will be omitted. That
is, the reception circuit 30 has the structure in which the
initialization control unit 40 and the initialization unit 50 are
added to the structure shown in FIG. 1 or FIG. 4. Further, the
input signal A and the signals B and C from the transmission
circuit 10 are the same as those shown in FIG. 5.
[0071] Reception signals F and G received from the transmission
circuit 10 via the non-contact transmission channel 20 are input to
the restoration circuit 35. The restoration circuit 35 restores the
input signal A on the basis of the reception signals F and G. That
is, the restoration circuit 35 generates the output signal L
corresponding to the input signal A. For the process in the
restoration circuit 35, the same process as that shown in FIG. 1 to
FIG. 5 can be used. That is, the restoration circuit 35 includes a
comparator and a widening circuit.
[0072] As shown in FIG. 7, a differential voltage F-G between the
signal F and the signal G includes edge pulses (main pulses) P1 and
P3 and counter pulses P2 and P4. The restoration circuit 35
transmits a signal to the initialization control unit 40. The
initialization control unit 40 distinguishes between a necessary
part for the signal restoration and an unnecessary part from the
signal and transmits a discrimination result to the initialization
unit 50 as an initialization control signal M. In accordance with
the initialization control signal M transmitted from the
initialization control unit 40, the initialization unit 50
initializes the signal F and the signal G of the non-contact
transmission channel 20.
[0073] Note that it is necessary to cause a swinging-back component
(broken line of F-G) in the differential voltage between the signal
F and the signal G from the non-contact transmission channel 20 to
avoid interfering with the next edge pulse. For this reason, for
example, after the counter pulse P2, the initialization control
signal M terminates an initialization instruction before the next
edge pulse P3 gets thereto at the latest. At the same time, the
capability of the initialization unit 50 is adjusted to cause the
signal F and the signal G to be attenuated to such an extent that a
signal intensity falls below a lower limit thereof that allows the
restoration circuit 35 to be operated by an initialization
operation. As a specific example, the initialization control unit
40 includes an OR (logical add) circuit with the signal F and the
signal G as inputs. Further, the initialization unit 50 includes a
transistor as a switch. Further, the transistor of the
initialization unit 50 connects a terminal F and a terminal G on an
output side of the non-contact transmission channel 20. By an
initialization control signal F from the initialization control
unit 40, the transistor switches on/off.
[0074] In this embodiment, when the edge pulse of the signal F-G is
input to the restoration circuit 35, the initialization control
signal M is output from the initialization control unit 40. A
condition of outputting the initialization control signal M is that
an edge pulse of a signal to be input reaches the restoration
circuit 35. For example, after the edge pulse P1 reaches the
circuit, all signal components before the next edge pulse P3
reaches the circuit are unnecessary for the restoration operation.
To a gate of the transistor of the initialization unit 50, the
initialization control signal M from the initialization control
unit 40 is input. On the basis of the initialization control signal
M, the initialization unit 50 short-circuits the terminal F and the
terminal G. By this operation, the initialization unit 50 forcibly
attenuates the reception signal unnecessary for the
restoration.
[0075] As a result, even if an interval between adjacent pulses is
reduced, an interference between the pulses becomes unlikely to
occur. Thus, it is possible to reduce a delay between the input and
the output and achieve a higher data rate. Note that the signal
transmitted from the restoration circuit 35 to the initialization
control unit 40 may be the very input signal of the restoration
circuit 35, for example, in addition to an internal waveform of the
restoration circuit 35. Alternatively, it is possible to take the
signal from any terminal appropriate to generate the initialization
control signal M. Further, the initialization control unit 40 is
not limited to the OR circuit. For example, the initialization
control unit 40 can be an AND circuit. The initialization unit 50
is not limited to the transistor that connects the terminal F and
the terminal G. For example, the initialization unit 50 may be a
transistor that individually connects the terminal F and the
terminal G with a reference potential.
[0076] Subsequently, detailed structures and operations of the
non-contact transmission channel 20 and the reception circuit 30 of
the communication device 100 according to this embodiment will be
described with reference to FIG. 8 to FIG. 10. FIG. 8 is a circuit
diagram showing an example of the structure of the communication
device 100. FIG. 9 is a timing chart showing signal waveforms in
the case where the initialization is not performed. FIG. 10 is a
timing chart showing signal waveforms in the case where the
initialization is performed.
[0077] The transmission circuit 10 includes an edge generation
circuit 11 and an edge generation circuit 12. The edge generation
circuit 11 detects a rising edge of a pulse included in the input
signal A and generates an edge pulse corresponding to the detected
rising edge. The edge generation circuit 11 detects a falling edge
of a pulse included in the input signal A and generates an edge
pulse corresponding to the detected falling edge.
[0078] From the transmission circuit 10, the signal B and the
signal C are transmitted to the non-contact transmission channel
20. The non-contact transmission channel 20 includes the primary
side coil 21 and the secondary side coil 22. The primary side coil
21 and the secondary side coil 22 are insulation transformers with
an insulation boundary intervened therebetween. That is, the
primary side coil 21 and the secondary side coil 22 are AC coupling
elements that are AC-coupled. To one end of the primary side coil
21, the signal B is supplied, and to the other end thereof, the
signal C is supplied. Therefore, a current corresponding to a
differential voltage between the signal B and the signal C flows
through the primary side coil 21. At timing of a rising edge of an
input signal IN or a falling edge thereof, a pulse-like current
flows through the primary side coil 21. Further, a direction of the
current that flows through the primary side coil 21 at the rising
edge of the input signal IN is opposite to a direction of a current
that flows through the primary side coil 21 at the falling edge.
Thus, it is possible to convert edge information of the input
signal A to the polarity of the transmission pulse.
[0079] Thus, in the secondary side coil 22, a differential voltage
corresponding to the current that flows through the primary side
coil 21 is induced. In a differential signal F-G, an edge pulse
corresponding to the edge of the input signal IN and a counter
pulse that appears immediately after the edge pulse exist. The
polarity of the counter pulse is opposite to that of the edge
pulse. In the differential signal F-G, the edge pulse P1 having the
positive polarity corresponding to the rising edge of the input
signal IN and the edge pulse P3 having the negative polarity
corresponding to the falling edge of the input signal IN exist.
Further, immediately after the edge pulse P1 having the positive
polarity, the counter pulse P2 having the negative polarity exists,
and immediately after the edge pulse P3 having the negative
polarity, the counter pulse P4 having the positive polarity
exists.
[0080] One end of the secondary side coil 22 is connected to a
filter 23, and the other end thereof is connected to a filter 24.
The filter 23 and the filter 24 are high-pass filters (HPF)
includes R and C, for example. The filter 23 and the filter 24
remove a noise component from a reception pulse received via the
non-contact transmission channel 20. The signal F and the signal G
that have passed through the filter 23 and 24 are output to the
reception circuit 30.
[0081] The reception circuit 30 includes the restoration circuit
35, the initialization control unit 40, and the initialization unit
50. The restoration circuit 35 includes comparators 31 and 32,
widening circuits 33 and 34, and a determination circuit 36. In the
comparator 31, the signal F that has passed through the filter 23
is input to the non-inverting input terminal, and the signal G that
has passed through the filter 24 is input to the inverting input
terminal. Therefore, the comparator 31 detects a pulse having the
positive polarity in the differential voltage F-G. An output of the
comparator 31 shows a waveform of a signal H shown in FIGS. 9 and
10. In the comparator 32, the signal F that has passed through the
filter 23 is input to the inverting input terminal, and the signal
G that has passed through the filter 24 is input to the
non-inverting input terminal. Therefore, the comparator 32 detects
a pulse having the negative polarity in the differential voltage
F-G. An output of the comparator 32 shows a waveform of a signal I
shown in FIGS. 9 and 10. The comparators 31 and 32 are differential
amplifiers with both ends of the secondary side coil 22 as
differential inputs.
[0082] The signal H from the comparator 31 is input to the widening
circuit 33. The signal I from the comparator 32 is input to the
widening circuit 34. The widening circuit 33 and the widening
circuit 34 increase pulse widths of the input signals H and I,
respectively. That is, the widening circuit 33 and the widening
circuit 34 are delay circuits that output the rising edge at a high
speed and delay and output the falling edge. With this structure,
it is possible to delay the falling edge of the pulse. Therefore,
the widening circuit 33 increases and outputs the pulse width of
the pulse of the signal H as a signal J to the determination
circuit 36. The widening circuit 34 increases the pulse width of
the pulse of the signal I and outputs the pulse as a signal K to
the determination circuit 36. The output from the widening circuit
33 and the output from the widening circuit 34 show signal
waveforms of the signal J and the signal K shown in FIGS. 9 and 10,
respectively.
[0083] The widening circuits 33 and 34 respectively output the
signal J and signal K to the determination circuit 36. The
determination circuit 36 includes a logic circuit that determines
which pulse get thereto first. That is, the determination circuit
36 determines which pulse of the signal J and the signal K gets
thereto first. The determination circuit 36 has the same structure
as the determination circuit 236 shown in FIG. 1, so a description
thereof will be omitted.
[0084] The initialization control unit 40 includes an OR circuit.
Specifically, the initialization control unit 40 is a NOR circuit.
To the initialization control unit 40, the signal J and the signal
K are input. That is, the initialization control unit 40 outputs
NOR of the signal J and the signal K as the initialization control
signal M to the initialization unit 50.
[0085] The initialization unit 50 has a transistor disposed between
the terminal F and the terminal G. More specifically, a source of a
Pch transistor is connected to the terminal F and a drain thereof
is connected to the terminal G. The initialization control signal M
from the initialization control unit 40 is input to a gate of the
transistor. Therefore, on the basis of the initialization control
signal M, the transistor is subjected to on/off control. When the
transistor as a switch is turned on, the terminal F and the
terminal G are short-circuited.
[0086] In the differential voltage F-G, swinging back of the
counter pulse occurs (see, signal F-G shown in FIG. 9 and FIG. 10).
In the case where the initialization is not performed, due to the
swinging back, for the signal H and signal I, pulses P5 and P6
unnecessary for the restoration are generated (see, signal H and
signal I shown in FIG. 9).
[0087] In the case where the initialization is not performed, when
the pulses of the signal H and the signal I are widened, the signal
J and the signal K are unnecessarily extended. For example, as
shown in FIG. 9, a period T1 is extended, a period T2 is shortened.
The period T1 is such a period that OR of the signal J and the
signal K becomes Hi and is a minimum required forbidden area for
the signal restoration. On the basis of the period T1, a limit of a
delay reduction is determined. Further, the period T2 is such a
period that OR of the signal J and the signal K becomes Lo and is a
timing margin to make it possible to recognize the next edge.
[0088] On the other hand, in the case where the initialization is
performed, at a timing of the swinging back of the counter pulses
P2 and P4, the initialization is performed. As shown in FIG. 10,
the pulses P5 and P6 unnecessary for the signal restoration are
removed from the signal H and the signal I. When the widening
circuits 33 and 34 widen the pulses of the signal H and the signal
I, the signal J and the signal K show waveforms as shown in FIG.
10. The period T1 in which OR of the signal J and the signal K
becomes Hi becomes shorter as compared to the case where the
initialization is not performed. Therefore, it is possible to
shorten the forbidden area and reduce a delay time of the pulse. It
is possible to extend the period T2 in which OR of the signal J and
the signal K becomes Lo, and the timing margin for recognizing the
edge is increased. That is, it is possible to suppress a reduction
of a timing margin and restore the signal with high accuracy.
[0089] In this way, by providing the initialization control unit 40
and the initialization unit 50 on the reception circuit 30 side, it
is possible to reliably restore the signal. For example, the
initialization control unit 40 detects a necessary part and an
unnecessary part from the reception signal, and on the basis of the
detection result, outputs an initialization control signal to the
initialization unit 50. On the basis of the initialization control
signal, the initialization unit 50 initializes the reception
signal. As a result, during a certain period after the edge pulse,
the signal F and the signal G are initialized. It is possible to
remove the unnecessary pulses P5 and P6 generated after the counter
pulse due to the swinging back. Therefore, it is possible shorten
the period T1 that is minimum required for the signal recovery, and
shorten the delay. Further, it is possible to achieve the higher
data rate.
[0090] Further, the initialization unit 50 includes a transistor
that is on/off controlled by the initialization control signal M.
With this structure, the initialization unit 50 can start or
terminate the initialization at an appropriate timing. The
transistor of the initialization unit 50 electrically connects the
terminal F with the terminal G. As a result, it is possible to
simplify the circuit structure. Further, by using the OR circuit
for the initialization control unit 40, it is possible to simplify
the circuit structure. Of course, the structure of the
initialization control unit 40 is not limited to the OR circuit,
and an AND circuit may be used therefor.
Second Embodiment
[0091] The communication device 100 according to this embodiment
will be described with reference to FIG. 11. FIG. 11 is a block
diagram showing the structure of the communication device 100
according to this embodiment. In this embodiment, a pulse width
adjustment circuit 60 and a delay circuit 70 are additionally
provided with respect to the structure in the first embodiment.
Note that the structure except the pulse width adjustment circuit
60 and the delay circuit 70 are the same as the structure in the
first embodiment, so a description thereof will be omitted as
appropriate.
[0092] The pulse width adjustment circuit 60 and the delay circuit
70 are disposed between the initialization control unit 40 and the
initialization unit 50. The pulse width adjustment circuit 60
adjusts a pulse width of the initialization control signal
generated by the initialization control unit 40. The delay circuit
70 delays an initialization control signal adjusted by the pulse
width adjustment circuit 60. Then, an initialization control signal
N delayed by the delay circuit 70 is input to the initialization
unit 50. On the basis of the initialization control signal N, the
initialization unit 50 short-circuits the terminal F and the
terminal G, thereby performing the initialization of the signal F
and the signal G. As a result, it is possible to obtain the same
effect as the first embodiment.
[0093] Further, in this embodiment, by providing the pulse width
adjustment circuit 60, it is possible to adjust a period during
which the initialization is performed. Further, by providing the
delay circuit 70, it is possible to adjust a timing when the
initialization is started. Thus, it is possible to optimize the
timing when the initialization unit 50 performs the initialization
and the period therefor, with the result that the signal can be
more reliably restored. As a result, it is possible to shorten the
delay and achieve the higher data rate.
[0094] In the first embodiment, the initialization operation in the
initialization unit 50 is performed on the basis of the
initialization control signal M from the initialization control
unit 40. That is, in accordance with an instruction of the
initialization control signal M, the initialization unit 50 turns
the transistor on. Therefore, in the case where the initialization
period is insufficient, the pulse width adjustment circuit 60
extends the pulse width of the initialization control signal M. In
contrast, in the case where the initialization period is excessive,
the pulse width adjustment circuit 60 reduces the pulse width of
the initialization control signal M. In this way, the pulse width
adjustment circuit 60 can arbitrarily set the pulse width.
[0095] Similarly, in the case where the timing when the
initialization is started is too fast, the delay circuit 70 sets
the delay time to be longer, thereby delaying an arrival time of
the pulse of the initialization control signal M. In contrast, in
the case where the timing when the initialization is started is too
late, the delay circuit 70 reduces the delay time, thereby bringing
the arrival time of the initialization pulse forward. In this way,
the delay circuit 70 can arbitrarily set the initialization start
timing.
[0096] Signal waveforms output from the pulse width adjustment
circuit 60 and the delay circuit 70 will be described with
reference to FIG. 12. FIG. 12 is a timing chart showing waveforms
at terminals M and N of the communication device 100 and a waveform
of a differential voltage of F-G. Note that, in FIG. 12, F-G shows
the signal waveform in the case where the initialization is not
performed, and F-G' shows a signal waveform in the case where the
initialization is performed. Further, in FIG. 12, M shows a signal
waveform in the case where the initialization control unit 40 is
the OR circuit, and M' shows a signal waveform in the case where
the initialization control unit 40 is the AND circuit.
[0097] As indicated by M and M' shown in FIG. 12, depending on the
structure of the initialization control unit 40, the pulse width
and the timing of the initialization control signal differs. In
order to appropriately perform the initialization, it is necessary
to output such a pulse as to be timed to the swinging back of the
differential voltage F-G to the initialization unit 50. Therefore,
the pulse width adjustment circuit 60 and the delay circuit 70
adjust the pulse width and the timing of the initialization control
signal M, with the result that the initialization control signal N
shown as N in FIG. 12 is supplied to the initialization unit
50.
[0098] By the initialization control signal N shown in FIG. 12, the
transistor of the initialization unit 50 is subjected to the on/off
control. As a result, like the signal F-G' shown in FIG. 12, the
swing back of the differential voltage can be appropriately
attenuated or deleted. Thus, it is possible to reliably restore the
input signal A from the signal L (not shown in FIG. 12).
[0099] Note that, in FIG. 11, the pulse width adjustment circuit 60
and the delay circuit 70 are disposed between the initialization
control unit 40 and the initialization unit 50, but the structure
and the arrangement of the pulse width adjustment circuit 60 and
the delay circuit 70 are not limited to those of FIG. 11. For
example, the structure is not limited to the structure in which the
pulse width adjustment circuit 60 and the delay circuit 70 are
provided independently of the restoration circuit 35, but can use a
part of the restoration circuit 35. For example, the widening
circuits 233 and 234 as shown in FIG. 1 or the widening circuits 33
and 34 as shown in FIG. 8 can be partly used to structure the pulse
width adjustment circuit 60 and the delay circuit 70. That is, the
pulse width adjustment circuit 60 and the delay circuit 70 may be
provided on a former stage of the initialization control unit
40.
[0100] Here, with reference to FIG. 13 to FIG. 15, the structure in
which a part of the widening circuits 33 and 34 is used as the
pulse width adjustment circuit 60 and the delay circuit 70 will be
described. FIG. 13 is a circuit diagram showing a part of the
reception circuit 30. FIG. 14 is a circuit diagram showing the
structure of the widening circuits 33 and 34 provided to the
reception circuit 30. FIG. 15 is a circuit diagram showing a
transistor structure of a comparator provided to the widening
circuits 33 and 34.
[0101] First, the structure of main parts of the communication
device 100 will be described with reference to FIG. 13. FIG. 13 is
a diagram showing the circuit structure from the HPFs 23 and 24 to
the determination circuit 36. Note that the structure of the main
parts of the communication device 100 is the same as above, so a
description thereof will be omitted as appropriate.
[0102] As in the structure shown in FIG. 8, the signals H and J
from the comparators 31 and 32 are input to the widening circuits
33 and 34, respectively. Further, to the widening circuits 33 and
34, a reference voltage VREF is input. The widening circuits 33 and
34 use the reference voltage VREF to increase the pulse width. The
widening circuit 33 outputs a signal Y1 to the initialization
control unit 40 and outputs the signal J to the determination
circuit 36. The widening circuit 34 outputs a signal Y2 to the
initialization control unit 40 and outputs the signal K to the
determination circuit 36. The determination circuit 36 has the same
structure as shown in FIG. 1. Then, the determination circuit 36
determines which of the signal J and the signal K gets thereto
first. Then, on the basis of the determination result of the
determination circuit 36, the input signal is restored.
[0103] The initialization control unit 40 is the NOR circuit as in
FIG. 8. The initialization control unit 40 outputs NOR of the
signal Y1 and the signal Y2 to the initialization unit 50 as the
initialization control signal N. The initialization unit 50
includes a Pch transistor as in FIG. 8. A source of the transistor
of the initialization unit 50 is connected to the terminal G, and a
drain thereof is connected to the terminal F. To a gate of the
transistor of the initialization unit 50, the initialization
control signal N is input.
[0104] The structures of the widening circuits 33 and 34 are shown
in FIG. 14. Note that the structures of the widening circuits 33
and 34 are the same, so a description will be given on the
assumption that the circuit shown in FIG. 14 is the widening
circuit 33. In other words, the widening circuit 34 has the same
circuit structure as that shown in FIG. 14, and to the widening
circuit 34, the signal I is input instead of the signal H. The
widening circuit 34 outputs the signal K instead of the signal J
and outputs the signal Y2 instead of the signal Y1.
[0105] To the widening circuit 33, the signal H and the reference
voltage VREF are input. The widening circuit 33 has comparators
COM1 to COM3, inverters INV1 and INV2, and NAND circuits NAND1 and
NAND2. The reference voltage VREF is input to the comparators COM1
to COM3.
[0106] The comparator COM1 compares the signal H with the reference
voltage VREF. The comparator COM1 outputs a comparison signal that
indicates a comparison result to the comparator COM2. The
comparator COM2 compares the output of the comparator COM1 with the
reference voltage VREF. The comparator COM2 outputs a comparison
signal to the NAND circuit NAND1 via the inverter INV1. The NAND
circuit NAND1 outputs NAND of the signal H and the output signal of
the inverter INV1 to the inverter INV2, the comparator COM3, and
the NAND circuit NAND2.
[0107] The inverter INV2 inverts the signal from the NAND circuit
NAND1 and outputs the inverted signal as the signal Y1. The
comparator COM3 compares the signal from the NAND circuit NAND1
with the reference voltage VREF. Then, the comparator COM3 outputs
a comparison signal to the NAND circuit NAND2. The NAND circuit
NAND2 outputs NAND of the signal from the NAND circuit NAND1 and
the signal from the comparator COM3 as the signal J.
[0108] Therefore, the comparators COM1 and COM2, the inverter INV1,
and the NAND circuit NAND1 are common to the widening circuit 33
and the pulse width adjustment circuit 60. That is, the widening
circuit 33 and the pulse width adjustment circuit 60 share the
comparators COM1 and COM2, the inverter INV1, and the NAND circuit
NAND1.
[0109] Here, the structures of the comparators COM1 and COM2 are
shown in FIG. 15. Note that the structures of the comparators COM1
and COM2 are the same, so a description will be given on the
assumption that the circuit shown in FIG. 15 is the comparator
COM1.
[0110] The comparator COM1 includes transistors Tr1 to Tr5. The
transistors Tr1 and Tr4 are Pch transistors. The transistor Tr2,
Tr3, and Tr5 are Nch transistors. Between a power supply voltage
VCC and a ground GND, the transistors Tr1 to Tr3 are connected in
series with one another.
[0111] Specifically, to a source of the transistor Tr1, the power
supply voltage VCC is supplied. A drain of the transistor Tr1 and a
drain of the transistor Tr2 are connected with each other. A source
of the transistor Tr2 and a drain of the transistor Tr3 are
connected with each other. A source of the transistor Tr3 is
connected to the ground GND. To a gate of the transistor Tr1 and a
gate of the transistor Tr2, the signal H is input. To a gate of the
transistor Tr3, a signal GN is input. The signal GN is the
reference voltage VREF.
[0112] Between the power supply voltage VCC and the ground GND, the
transistors Tr4 and Tr5 are connected in series with each other.
Specifically, to a source of the transistor Tr4, the power supply
voltage VCC is supplied. A drain of the transistor Tr4 and a drain
of the transistor Tr5 are connected with each other. A source of
the transistor Tr5 is connected to the ground GND. A voltage
between the drain of the transistor Tr1 and the drain of the
transistor Tr2 is input to a gate of the transistor Tr4 and a gate
of the transistor Tr5. A voltage between the drain of the
transistor Tr4 and the drain of the transistor Tr5 is output as an
output signal OUT. That is, when the assumption is made that the
circuit shown in FIG. 15 is the comparator COM1, the output signal
OUT is output to the comparator COM2. When the assumption is made
that the circuit shown in FIG. 15 is the comparator COM2, the
output signal OUT is output to the inverter INV1.
[0113] With this structure, to the initialization control unit 40,
the signals J and K that have been subjected to the pulse width
adjustment are input. Thus, the initialization unit 50 performs
initialization for the signal F and the signal G at an appropriate
timing. As a result, it is possible to adjust a timing of starting
the initialization operation and an initialization period
appropriately.
[0114] As described above, by using a part of the restoration
circuit 35, the pulse width and the timing can be adjusted. That
is, the pulse width adjustment circuit 60 and the delay circuit 70
share a part of the restoration circuit 35. With this structure, it
is possible to simplify a circuit to be added to adjust the pulse
width and the timing. Therefore, the circuit structure can be
simplified. Note that the structure of the circuit for adjusting
the timing and the pulse width the initialization control signal N
is not limited to the above structure. That is, it is only
necessary to provide a circuit capable of adjusting the timing when
the initialization is performed and the initialization period to
the reception side.
Third Embodiment
[0115] The communication device 100 according to this embodiment
will be described with reference to FIG. 16. FIG. 16 is a block
diagram showing the structure of the communication device 100. In
this embodiment, the filters 23 and 24 are not provided to the
non-contact transmission channel 20. That is, to the secondary side
coil 22, the initialization unit 50 is directly connected. Note
that the structure except the non-contact transmission channel 20
is the same as the above embodiments, so a description thereof will
be omitted as appropriate.
[0116] The communication device 100 includes the transmission
circuit 10, the non-contact transmission channel 20, the
restoration circuit 35, the initialization control unit 40, and the
initialization unit 50. The transmission circuit 10 converts the
input signal A into a pulse. The non-contact transmission channel
20 has the primary side coil 21 and the secondary side coil 22 as
the AC coupling elements. The non-contact transmission channel 20
transmits the pulse from the transmission circuit 10 in a
non-contact manner. On the basis of the reception signals F and G
corresponding to the pulses transmitted through the non-contact
transmission channel 20, the restoration circuit 35 restores the
input signal A. The initialization unit 50 initializes an output of
the non-contact transmission channel 20. On the basis of a
reception signal corresponding to the pulse received through the
non-contact transmission channel 20, the initialization control
unit 40 outputs a control signal that controls the initialization
unit 50.
[0117] An example of signal waveforms of the communication device
100 is shown in FIG. 17. FIG. 17 is a timing chart showing signal
waveforms at terminals. As described above, in order to prevent a
timing margin between edge pulses input to the restoration circuit
35 from being reduced, the initialization unit 50 performs
initialization. In the case where the non-contact transmission
channel 20 does not include the filters 23 and 24, the swinging
back of the counter pulse that causes a reduction of the timing
margin is not generated. However, even in the case where the
swinging back due to a transient property of the counter pulse is
not generated, a ringing may occur in the differential voltage F-G
(see, F-G shown in FIG. 17). For example, due to the ringing of the
reception signal caused by an inductance of the secondary side coil
22, the timing margin is also reduced. In this case, as shown in
FIG. 7, the initialization is performed immediately after the
secondary side coil 22, with the result that it is possible to
suppress the reduction of the timing margin.
[0118] Therefore, as in the first embodiment, on the basis of the
signal from the restoration circuit 35, the initialization control
unit 40 generates the initialization control signal M (see, M shown
in FIG. 17). Then, when the initialization unit 50 performs the
initialization for the signal F and the signal G on the basis of
the initialization control signal M, the differential voltage F-G'
after the initialization shows a waveform of F-G' of FIG. 17. As a
result, it is possible to obtain the same effect as the first
embodiment.
[0119] Note that, as a non-contact transmission system, there are
various methods for the signal restoration. For example, (1) the
signal restoration based on the pulse polarity as described in the
first embodiment, (2) signal restoration based on a pulse count,
(3) signal restoration by a Set/Reset circuit, and the like can be
provided. The operation of the signal initialization according to
this embodiment can be used for any one of the above items (1) to
(3). This point will be described as follows.
[0120] (1) Signal Restoration Based on Pulse Polarity
[0121] An example of the structure of restoring a signal on the
basis of the pulse polarity is shown in FIG. 18. FIG. 18 is a
diagram simply showing a circuit structure in which the signal is
restored on the basis of the pulse polarity. Note that FIG. 18
shows only one system of an input of the primary side coil 21 and
an output of the secondary side coil 22.
[0122] As described above, on the basis of a signal from the
comparator 31, the determination circuit 36 determines which pulse
gets thereto first. Signal waveforms in the structure shown in FIG.
18 are shown in FIG. 19. FIG. 19 shows signal waveforms in the case
where the signal is restored normally and signal waveforms in the
case where an abnormality occurs for the restoration due to the
swinging back. By an edge detection of an input signal, the signal
A is supplied to the primary side coil 21. By the signal A, when a
current flows through the primary side coil 21, the signal B is
generated in the secondary side coil 22.
[0123] In (1) the signal restoration based on the pulse polarity,
it is necessary to separate the counter pulse from the edge pulse
to be identified. The signal B is largely affected by the swinging
back of the counter pulse. For this reason, in the (1) restoration
based on the pulse polarity, more effects of the initialization are
obtained as compared to the (2) restoration based on the pulse
count and the (3) signal restoration by the Set/Reset.
[0124] For example, the swinging back is caused between the edge
pulses to be identified. Due to the swinging back, the pulses are
stuck together, and an amplitude is reduced. This causes an output
abnormality. However, as described in the first to third
embodiments, by performing the initialization, it is possible to
delete or attenuate the swinging back. Thus, it is possible to
restore the signal normally.
[0125] (2) Signal Restoration Based on Pulse Count
[0126] An example of the structure of the (2) signal restoration
based on the pulse count is shown in FIG. 20. FIG. 20 is a diagram
simply showing a circuit structure in which the signal is restored
on the basis of the pulse count. Note that FIG. 20 shows only one
system of an input of the primary side coil 21 and an output of the
secondary side coil 22. In FIG. 20, an output of the comparator 31
is input to a counter 41. The counter 41 restores the signal by
counting the edge pulses.
[0127] In the case where the (2) signal restoration based on the
pulse count is performed, the counter pulse does not affect the
restoration. However, when the swinging back of the counter pulse
occurs, the swinging back may interfere with a subsequent edge
pulse. Thus, as shown in FIG. 21, when the swinging back interferes
with the subsequent edge pulse, the edge pulse count is decreased.
In the case where the signal is restored on the basis of the pulse
count, the signal is initialized as described in the first to third
embodiments, with the result that the swinging back can be deleted
or attenuated. As a result, it is possible to correctly restore the
signal.
[0128] (3) Signal Restoration by Set/Reset
[0129] The structure of the (3) signal restoration by a Set/Reset
will be shown in FIG. 22. FIG. 22 is a diagram simply showing a
circuit structure in which the signal is restored by the Set/Reset.
Note that in the structure shown in FIG. 22, in the non-contact
transmission channel 20, two primary side coils 21a and 21b and two
secondary side coils 22a and 22b are provided. Further, The
restoration circuit 35 includes comparators 31a and 31b. A signal B
from the secondary side coil 22a is input to the comparator 31a. A
signal B' from the secondary side coil 22b is input to the
comparator 31b. Outputs of the comparators 31a and 31b are input to
an SR logic circuit 42. The SR logic circuit 42 includes an SR
latch circuit and restores the input signal on the basis of the
outputs of the comparator 31a and 31b.
[0130] In the case where the (3) signal restoration by the
Set/Reset is performed, the counter pulse does not affect the
restoration. However, when the swinging back of the counter pulse
occurs, the pulse may interfere with a subsequent edge pulse. For
example, when the swinging back of the counter pulse occurs, the
edge pulse of the output B and the pulse of an output B' (swinging
back) are temporally stuck together. Therefore, as shown in FIG.
23, when the swinging back causes the interference with the
subsequent edge pulse, the signal is erroneously restored. In the
case of the structure shown in FIG. 22, by initializing the signal
as described in the first to third embodiments, it is possible to
delete or attenuate the swinging back. As a result, it is possible
to correctly restore the signal.
Application Example
[0131] The communication device 100 according to this embodiment
can be applied to an inverter device that drives a motor by being
used as an isolator. FIG. 24 is a diagram showing the structure in
the case where the communication device 100 according to this
embodiment is applied to an inverter device by being used as an
isolator.
[0132] The inverter device shown in FIG. 24 has a low-voltage
circuit 110 and a high-voltage circuit 120. The low-voltage circuit
110 is operated with a low voltage of approximately 5 V, for
example. The high-voltage circuit 120 is operated with a high
voltage of approximately 1 kV, for example. That is, the inverter
device is separated into the low-voltage circuit 110 and the
high-voltage circuit 120. The low-voltage circuit 110 and the
high-voltage circuit 120 are isolated by the communication device
100 as the isolator. That is, the primary side coil 21 side of the
communication device 100 corresponds to the low-voltage circuit
110, and the secondary side coil 22 side corresponds to the
high-voltage circuit 120 with a boundary set between the primary
side coil 21 and the secondary side coil 22.
[0133] The low-voltage circuit 110 includes a micro controller
(MCU) 111. The high-voltage circuit 120 includes a gate driver 121,
an IGBT 122, and a motor 123. The micro controller 111 generates
transmission data on the basis of an instruction from a peripheral
device or a console. The micro controller 111 outputs, for example,
transmission data that has been subjected to PWM modulation to the
communication device 100. Note that the motor 123 is a three-phase
motor driven with a U phase, a V phase, and a W phase, so the
communication device 100 is provided for each of UH, UL, VH, VL,
WH, and WL. Note that the gate driver 121 and the IGBT 122 are also
provided for each of UH, UL, VH, VL, WH, and WL. That is, the
communication device 100, the gate driver 121, and the IGBT 122 are
provided for six systems.
[0134] The communication device 100 outputs a signal to the gate
driver 121. On the basis of the signal from the communication
device 100, the gate driver 121 drives the IGBT 122. The IGBT 122
supplies a current that flows through the motor 123. As a result,
it is possible to control the motor 123 in an analog manner on the
basis of the transmission data generated by the micro controller
111.
[0135] As described above, on the basis of the signal from the
restoration circuit 35, the communication device 100 performs the
signal initialization. Thus, it is possible to reliably restore the
signal and more correctly drive the motor 123. Note that in the
above description, the communication device 100 is used as the
isolator, but the communication device 100 is not limited to the
isolator, as long as the communication device 100 includes the
non-contact transmission channel.
[0136] A (The) program can be stored and provided to a computer
using any type of non-transitory computer readable media.
Non-transitory computer readable media include any type of tangible
storage media. Examples of non-transitory computer readable media
include magnetic storage media (such as floppy disks, magnetic
tapes, hard disk drives, etc.), optical magnetic storage media
(e.g. magneto-optical disks), CD-ROM (compact disc read only
memory), CD-R (compact disc recordable), CD-R/W (compact disc
rewritable), and semiconductor memories (such as mask ROM, PROM
(programmable ROM), EPROM (erasable PROM), flash ROM, RAM (random
access memory), etc.). The program may be provided to a computer
using any type of transitory computer readable media. Examples of
transitory computer readable media include electric signals,
optical signals, and electromagnetic waves. Transitory computer
readable media can provide the program to a computer via a wired
communication line (e.g. electric wires, and optical fibers) or a
wireless communication line. (The first and second embodiments can
be combined as desirable by one of ordinary skill in the art.)
[0137] Further, the structures of the first to third embodiments
described above can be combined and used as appropriate. A part or
all of the above embodiments can be described as the following
notes but are not limited to those.
[0138] (Note 1)
[0139] A communication device including:
[0140] a transmission circuit that converts an input signal into a
pulse;
[0141] a non-contact transmission channel that includes an AC
coupling element and transmits the pulse from the transmission
circuit in a non-contact manner;
[0142] a restoration circuit that restores the input signal on a
basis of a reception signal corresponding to the pulse transmitted
via the non-contact transmission channel;
[0143] an initialization unit that initializes an output of the
non-contact transmission channel; and
[0144] an initialization control unit that outputs a control signal
of controlling the initialization unit on a basis of the reception
signal corresponding to the pulse received via the non-contact
transmission channel.
[0145] (Note 2)
[0146] The communication device according to Note 1, further
including a widening circuit that increases a pulse width of the
pulse received via the non-contact transmission channel,
[0147] in which the restoration circuit restores the input signal
on a basis of the received pulse, the pulse width of which is
increased by the widening circuit.
[0148] (Note 3)
[0149] The communication device according to Note 1, further
including a circuit that adjusts at least one of a timing and a
period of the initialization performed by the initialization
unit.
[0150] (Note 4)
[0151] The communication device according to Note 1, in which the
initialization unit is connected to both ends of the AC coupling
element on a reception side of the non-contact transmission
channel.
[0152] (Note 5)
[0153] The communication device according to Note 1, in which
[0154] the initialization unit includes a transistor connected to a
reception side of the non-contact transmission channel,
[0155] the initialization control unit performs on/off control for
the transistor, and
[0156] the transistor is turned on, thereby performing
initialization.
[0157] (Note 6)
[0158] The communication device according to Note 1, in which
[0159] the reception signal includes a main pulse and a counter
pulse corresponding to the pulses transmitted through the
non-contact transmission channel,
[0160] the counter pulse has a polarity opposite to the main pulse
and is continuous with the main pulse, and
[0161] the restoration circuit restores the input signal in
accordance with the polarity of the main pulse.
[0162] (Note 7)
[0163] The communication device according to Note 1, in which, to
the non-contact transmission channel, a high-pass filter connected
to the AC coupling element is provided.
[0164] (Note 8)
[0165] A communication method including:
[0166] converting an input signal into a pulse in a transmission
circuit;
[0167] transmitting the pulse from the transmission circuit to a
reception circuit in a non-contact manner via a non-contact
transmission channel including an AC coupling element;
[0168] restoring the input signal on a basis of a reception signal
corresponding to the pulse transmitted via the non-contact
transmission channel;
[0169] generating a control signal on a basis of the reception
signal corresponding to the pulse received via the non-contact
transmission channel; and
[0170] initializing an output of the non-contact transmission
channel on a basis of the control signal.
[0171] (Note 9)
[0172] The communication method according to Note 8, further
including:
[0173] increasing a pulse width of the pulse received via the
non-contact transmission channel; and
[0174] restoring the input signal on a basis of the received pulse,
the pulse width of which is increased.
[0175] (Note 10)
[0176] The communication method according to Note 8, further
including adjusting at least one of a timing and a period of
performing the initialization.
[0177] (Note 11)
[0178] The communication method according to Note 8, in which, to
both ends of the AC coupling element on a reception side of the
non-contact transmission channel, an initialization unit that
performs the initialization is connected.
[0179] (Note 12)
[0180] The communication method according to Note 8, in which
[0181] a transistor is connected to a reception side of the
non-contact transmission channel,
[0182] the transistor is on/off controlled in accordance with the
control signal, and
[0183] the initialization is performed by turning on the
transistor.
[0184] (Note 13)
[0185] The communication method according to Note 8, in which
[0186] the reception signal includes a main pulse and a counter
pulse corresponding to the pulses transmitted through the
non-contact transmission channel,
[0187] the counter pulse has a polarity opposite to the main pulse
and is continuous with the main pulse, and
[0188] the input signal is restored in accordance with the polarity
of the main pulse.
[0189] (Note 14)
[0190] The communication method according to Note 8, in which, to
the non-contact transmission channel, a high-pass filter connected
to the AC coupling element is provided.
[0191] (Note 15)
[0192] A receiver including:
[0193] a restoration circuit that restores an input signal on a
basis of a reception signal corresponding to a pulse transmitted
via a non-contact transmission channel including an AC coupling
element;
[0194] an initialization unit that initializes an output of the
non-contact transmission channel; and
[0195] an initialization control unit that outputs a control signal
of controlling the initialization unit on a basis of the reception
signal corresponding to the pulse received via the non-contact
transmission channel.
[0196] (Note 16)
[0197] The receiver according to Note 15, further including a
widening circuit that increases a pulse width of the pulse received
via the non-contact transmission channel,
[0198] in which the restoration circuit restores the input signal
on a basis of the received pulse, the pulse width of which is
increased by the widening circuit.
[0199] (Note 17)
[0200] The receiver according to Note 15, further including a
circuit that adjusts at least one of a timing and a period of the
initialization performed by the initialization unit.
[0201] (Note 18)
[0202] The receiver according to Note 15, in which the
initialization unit is connected to both ends of the AC coupling
element on a reception side of the non-contact transmission
channel.
[0203] (Note 19)
[0204] The receiver according to Note 15, in which
[0205] the initialization unit includes a transistor connected to a
reception side of the non-contact transmission channel,
[0206] the initialization control unit performs on/off control for
the transistor, and
[0207] the transistor is turned on, thereby performing the
initialization.
[0208] (Note 20)
[0209] The receiver according to Note 15, in which
[0210] the reception signal includes a main pulse and a counter
pulse corresponding to the pulses transmitted through the
non-contact transmission channel,
[0211] the counter pulse has a polarity opposite to the main pulse
and is continuous with the main pulse, and
[0212] the restoration circuit restores the input signal in
accordance with the polarity of the main pulse.
[0213] In the above, the invention carried out by the inventor of
the present invention is specifically described on the basis of the
embodiments. However, the present invention is not limited to the
embodiments described above and can of course be variously changed
without departing from the gist of the present invention.
[0214] While the invention has been described in terms of several
embodiments, those skilled in the art will recognize that the
invention can be practiced with various modifications within the
spirit and scope of the appended claims and the invention is not
limited to the examples described above.
[0215] Further, the scope of the claims is not limited by the
embodiments described above.
[0216] Furthermore, it is noted that, Applicant's intent is to
encompass equivalents of all claim elements, even if amended later
during prosecution.
* * * * *